Production of monosaccharides from poplar by a two-step hydrogen peroxide-acetic acid and sodium hydroxide pretreatment

•Effects of different HPAC pretreatment conditions on poplar were investigated.•Acetyl groups were completely removed from poplar by sodium hydroxide post-treatment.•33.3 % HPAC loading and 50 % time was saved by sodium hydroxide post-treatment.•A novel strategy was developed to reduce HPAC loading and improved safety of pretreatment. Hydrogen peroxide-acetic acid (HPAC) pretreatment can selectively remove lignin from biomass. However, high concentration of HPAC increases the cost of pretreatment and the risk of explosion. In this work, HPAC pretreatment was optimized and the function of the second-step sodium hydroxide pretreatment in the reduction of HPAC dosage and the increased of saccharification of poplar was investigated. The results showed that pretreatment of poplar with 75 % HPAC at 80 ˚C for 2 h with 100 mM H2SO4 as a catalyst removed 94.1 % of lignin, and the glucose and xylose yields of HPAC-pretreatd poplar by cellulase were 78.5 % and 66.3 %, respectively. After post-treatment with 1 % sodium hydroxide, the lignin removal in 50 % HPAC (80 ˚C, 1 h)-pretreated poplar increased from 47.7% to 86.7 % with the acetyl groups were completely removed. After sodium hydroxide pretreatment, the yields of glucose and xylose of 50 % HPAC-pretreated poplar largely increased from 37.8 % and 28.8 % to 79.4 % and 80.0 %, respectively. The data here indicated that alkaline treatment reduced about 33 % HPAC loading and 50 % reaction time without the decrease of hydrolysis yield. This work provided a novel strategy to efficient production of fermentable sugars from poplar with less HPAC loading and higher safety at mild conditions.